Diesel engines are widely used in commercial and military vehicles, as well as some light duty vehicles. The design compression ratio is a compromise between power, economy, emissions, and cold startability. The optimum ratio for best economy is near 14:1 to 15:1, whereas the necessary compression ratio for cold starting ranges from 16:1 to 23:1 depending on the specific design of the engine and its application. The cold starting ranges are too high for best economy, lowest emissions, and optimum power boost.